CN103488824A - Field operation optimization method for SCR (selective catalytic reduction) denitration system - Google Patents

Abstract

A field operation optimization method for an SCR (selective catalytic reduction) denitration system includes the steps of using a geometric center of an SCR denitration system reactor body as an origin of coordinates to establish a three-dimensional model of the SCR denitration system; meshing the three-dimensional model according to structural features of the SCR denitration system to obtain a mesh model; establishing a physical model for internal structure of the SCR denitration system, setting transfer equations for meshes in the mesh grid according to the physical model, and determining initial boundary conditions of the mesh grid; subjecting the SCR denitration system to field test so as to obtain smoke parameters of field operation of the SCR denitration system; introducing smoke parameters into the mesh model to allow for simulation reaction to acquire operational condition parameters of the SCR denitration system; subjecting the SCR denitration system to field operation parameter optimization according to the condition parameters. The method has the advantages that optimization cost can be reduced, optimization efficiency can be improved, and more accurate condition parameters can be obtained by changing meshing and parameter settings so that optimization accuracy can be improved.

Description

The on-the-spot operation of SCR denitrating system optimization method

Technical field

The present invention relates to the electric power project engineering field, particularly relate to the on-the-spot operation of a kind of SCR denitrating system optimization method.

Background technology

Atmospheric pollution is one of outstanding environmental problem of facing of the whole world, and be broadly divided into two large classes by the difference of pollutant existence: aerosol state pollutant and gaseous state pollutant, wherein the gaseous state pollutant comprises with SO ₂be main sulfocompound, with NO _xbe main nitrogen-containing compound, hydrocarbon and halogen compounds etc.Nitrogen-containing compound mainly contains NO, NO ₂, N ₂o, N ₂o ₃, N ₂o ₄, N ₂o ₅, the oxides of nitrogen generated in combustion process is mainly NO and NO ₂.

Along with atmosphere NO _xthe increase of concentration, a series of city and regional environment problem are more outstanding, health and ecologic environment are all formed to huge prestige evil, for this reason, within 2011, Chinese Ministry of Environmental Protection has issued up-to-date " fossil-fuel power plant atmospheric pollutant emission standard " (GB13223-2011), the pollutant emission of fuel-burning power plant has been proposed to requirements at the higher level: NO _xconcentration of emission be less than 100mg/Nm3, therefore, denitration in the stove technology and non-selection catalytic reduction (SNCR) denitration technology have been difficult to reach the requirement of new standard, and selective catalysis reduction (SCR) reaction denitration technology is because the characteristics that its system is simple and reliable, denitration efficiency is high are widely adopted.

(1) denitrating technique flow process: compressor is unloaded, Liquid Ammonia Storage, liquid ammonia gasification, be decompressed to denitrification apparatus, air distribution mixing, denitration reaction system, fan blower.

(2) major equipment (by two the public a set of ammonia of denitration unit station systems).

1) discharging compressor (totally 2);

Ammonia station system arranges 2 discharging compressors, a preparation and a use.The discharging compressor extracts the ammonia in storage ammonia tank, after compression the liquefied ammonia of tank car is pushed in liquid ammonia storage tank.Need select the compressor air-discharging amount during design, the saturated vapor pressure of liquefied ammonia in storage ammonia tank, liquefied ammonia unloads vehicle flowrate, the liquefied ammonia resistance of ducting and climate temperature etc. while unloading ammonia.

2) storage ammonia tank (at least two storage ammonia tanks);

The reservoir capacity of liquefied ammonia, should under design conditions, consider the denitrification apparatus operation of two stoves according to boiler BMCR operating mode, moves 20 hours every day, moves continuously the consumption of 7 days and consider.Excess flow valve, reverse checkvalve, emergency shutdown valve, safety valve, thermometer, tensimeter, liquid level gauge, high liquid level warning instrument and corresponding transmitter are installed on basin.The basin surrounding is equipped with service water spray pipe and nozzle, and when basin tank body excess Temperature, automatic spraying device starts, and the tank body automatic spray is lowered the temperature; Also can start automatic spraying device when having micro-ammonia to leak, ammonia is absorbed, control ammonia and pollute.

3) liquefied ammonia evaporator tank (2);

Liquefied ammonia evaporates needed heat and adopts Steam Heating that heat is provided, and pressure control valve is housed on evaporator ammonia pressure is controlled to certain limit, and evaporator also should be equipped with safety valve, can prevent that the equipment pressure anomaly is too high.Liquid ammonia evaporator should be according to 2 * 100% Capacity design (the using and the reserved) under the BMCR operating mode.

4) ammonia dashpot (1);

Enter the ammonia buffer tank from the ammonia flow of evaporator evaporation, by pressure regulator valve, reduce pressure into certain pressure, then deliver to the denitrating system of boiler side by the ammonia delivery line.The ammonia buffer tank should be able to meet the ammonia for SCR system supply pressure stability, avoids being subject to that evaporator operation is unstable affects.

5) ammonia dilution trap (1);

The ammonia thinning tank is certain volume tank, the liquid level of tank should be maintained by overflow line, the liquefied ammonia system enters from the thinning tank bottom after respectively discharging the ammonia of discharging in place and being collected by pipeline, by dispersion pipe, ammonia is dispensed in thinning tank, utilizes large water gaging to carry out the ammonia of the discharge such as absorption safety valve.

6) dilution air (every unit 2 Fans);

The ammonia that sprays into the reactor flue should be the mixed gas containing 5% left and right ammonia after Dilution air.Selected blower fan should meet and removes the peaked requirement of NOx in flue gas, and leaves certain surplus.Dilution air should arrange by two 100% capacity (the using and the reserved).

7) ammonia leakage detects security alerting system (cover);

Liquid Ammonia Storage and supply system periphery should be provided with the ammonia detecting device, to detect the leakage of ammonia, and show the concentration of Ammonia in Atmosphere.When detecting device records the Ammonia in Atmosphere excessive concentration, in denitrification apparatus synergic system control system and unit pulpit, can give the alarm, send on the spot the sound, warning blinker, to remind operating personnel, take necessary measure, occur with the abnormal conditions that prevent ammonia leakage.

8) nitrogen blowing system;

Purged by each equipment of nitrogen purge line Dui An district before the liquefied ammonia discharging, prevented that ammonia leakage and ammonia from mixing and causing danger with the air of remnants in system.

9) fire-fighting and safety installations;

Liquefied ammonia stores with feed region should arrange perfect fire-fighting system, eye syringe and gas mask etc.

1.SCR the problem that the numerical simulation quasi-solution is determined

In the design of SCR denitrating system, the option of catalyzer and reactor all will directly affect the runnability of SCR denitrating system, when reactor design is not good or it while moving under undesirable operating mode, even catalyst performance is good, the operation characteristic of this SCR denitrating system can not reach ideal state yet.

Generally, moving important technical matters at reactor is:

Catalyst inlet NH ₃/ NO _xcONCENTRATION DISTRIBUTION, spray ammonia grid (AIG) and ground floor catalyst inlet face velocity are uniform, and the motion of fly ash granule in Benitration reactor.

(1) NH ₃/ NO _xcONCENTRATION DISTRIBUTION;

NH3/NOx to be uniformly distributed the efficient operation to reactor be vital.If NH ₃/ NO _xskewness will produce NH in reactor ₃/ NO _xhigher zone, enter catalyst layer once mix inhomogeneous flue gas, high NH ₃/ NO _xthe flue gas zone can cause some negative effects, as produce too high the escaping of ammonia, the corrosion etc. that reduces system denitration rate and cause reactor downstream equipment.The time for ammonia-gas spraying device, set up flow model in design, and when operation, reactor to be carried out to regular test be all to solve NH ₃/ NO _xthe distribution effective method.

(2) spray ammonia grid (AIG) and catalyst inlet velocity uniformity are uniform;

The velocity distribution of optimizing inside reactor is a very important job of reactor design.The velocity distribution inequality not only can affect NH ₃/ NO _xdistribution, the more important thing is that this can cause the inordinate wear of catalyzer at high-speed region, also can cause and fly deposition and make sintering of catalyst at low-speed region simultaneously.Test bed and carry out numerical simulation work by reactor being built to cold conditions, optimize inside reactor guiding device and fairing and arrange, realize the uniform requirement of speed.

(3) motion of fly ash granule;

With speed distributing inhomogeneity sample, the fly ash granule skewness also can increase wearing and tearing and the dust stratification of catalyst in reactor.Can, by the method for numerical simulation, optimize Flow Field Distribution and realize the purpose that fly ash granule is uniformly distributed and effectively removes.

In order to obtain the duty parameter of SCR denitrating system operation, need to be tested at the scene, perhaps set up a set of entity physical simulating device and carry out the simulation reaction test, obtain relevant duty parameter, to control the operational factor of the on-the-spot SCR denitrating system moved, but no matter scene is tested or physical simulating device, cost is all higher, particularly the complicacy along with SCR denitrating system inner structure is higher, this problem is more obvious, simultaneously, all need to carry out the real reaction simulation test at every turn, cause the efficiency of field optimizing also lower.

Summary of the invention

Based on this, be necessary for high, the inefficient problem of above-mentioned cost, the on-the-spot operation of a kind of SCR denitrating system optimization method is provided, can reduce the on-the-spot operation of SCR denitrating system Cost optimization, improve field optimizing efficiency.

The on-the-spot operation of a kind of SCR denitrating system optimization method, comprise the steps:

The geometric center of SCR denitrating system reactor body of take is true origin, builds the three-dimensional model of SCR denitrating system;

According to the architectural feature of SCR denitrating system, described three-dimensional model is carried out to grid division and obtain grid model;

Set up the physical model of SCR denitrating system inner structure, according to described physical model, the equation of transfer between each grid in described grid model is set, and determine the initial boundary condition of described grid model;

The SCR denitrating system is carried out to site test, obtain the Gas Parameters of the on-the-spot operation of SCR denitrating system;

Described Gas Parameters is imported to described grid model and carry out simulation reaction, obtain the duty parameter of SCR denitrating system operation;

According to described duty parameter, the on-the-spot operational factor of SCR denitrating system is optimized.

The on-the-spot operation of above-mentioned SCR denitrating system optimization method, build the three-dimensional model of SCR denitrating system, obtain grid model by grid division, the Gas Parameters of on-the-spot operation, import grid model and carry out the duty parameter that simulation reaction obtains operation, the on-the-spot operational factor of SCR denitrating system is optimized.SCR denitrating system Three-dimensional simulation and field optimizing based on numerical simulation and site test combination, obtain duty parameter without adopting physical simulating device to test, can reduce Cost optimization, improve optimization efficiency, simultaneously, by changing, grid is divided and parameter arranges the higher duty parameter of acquisition accuracy, can improve the optimization accuracy.

The accompanying drawing explanation

The part-structure schematic diagram that Fig. 1 is the SCR denitrating system;

The on-the-spot operation of the SCR denitrating system that Fig. 2 is embodiment optimization method process flow diagram;

Fig. 3 is spray ammonia grid entrance section flue gas flow field distribution situation schematic diagram;

Fig. 4 is catalyst layer entrance section flue gas flow field distribution situation schematic diagram;

Fig. 5 is velocity distribution schematic diagram on cross-sectional width center line Z=0 and degree of depth center line X=0 two center lines;

Fig. 6 is catalyst inlet cross section ammonia CONCENTRATION DISTRIBUTION situation schematic diagram;

Fig. 7 is catalyst inlet cross section B flying dust CONCENTRATION DISTRIBUTION schematic diagram;

Fig. 8 sprays into the track following schematic diagram of particle in reactor on the diverse location grid surface.

Embodiment

Embodiment below in conjunction with accompanying drawing to the on-the-spot operation of SCR denitrating system of the present invention optimization method is described in detail.

Shown in figure 1, the part-structure schematic diagram that Fig. 1 is the SCR denitrating system, there is shown smoke inlet to the exhanst gas outlet part, comprise ash bucket, flue and reactor, wherein, be provided with rectifier, catalyst layer in reactor, its principle of work is: by the flue gas of uniform temperature, adding ammonia, under the effect of catalyzer, with NO optionally reduction reaction become N2 and H2O.

Shown in Figure 2, the on-the-spot operation of the SCR denitrating system that Fig. 2 is embodiment optimization method process flow diagram, mainly comprise the steps:

Step S101, the geometric center of SCR denitrating system reactor body of take is true origin, builds the three-dimensional model of SCR denitrating system.

In this step, can set up according to the SCR denitrating system of power plant the 3-D geometric model of 1:1 ratio, comprise ash bucket, flue and reactor, wherein, be provided with rectifier, catalyst layer in reactor, in this process, due to the catalyst structure complexity, and its honeycomb Ullage yardstick is much smaller than reactor dimensions, therefore, can regard catalyzer as formed by parallel channels not porous medium in the same way, in addition, fair water fin thickness and ammonia injection grid (AIG) vane thickness are also much smaller than reactor dimensions, therefore its thickness can be ignored.In concrete modeling, take the reactor body geometric center as true origin, model can be with reference to shown in figure 1, and wherein the A face is that ammonia sprays the front flue of entrance cross section, and the B face is cross section, the front place of ground floor catalyst inlet.

Step S102, according to the architectural feature of SCR denitrating system, carry out grid division to described three-dimensional model and obtain grid model.

In this step, consider the inner structure of model complexity, can, according to the architectural feature of SCR denitrating system inside, adopt structuring and non-structured hybrid grid to be divided zoning.

In one embodiment, can by the flue of the zoning of three-dimensional model, and reactor part with structured grid, divided, and by the flue fair water fin of the zoning of three-dimensional model, and the reactor inlet part with unstructured grid, divided.Total grid number of described grid model can be 1,500,000.

Step S103, set up the physical model of SCR denitrating system inner structure, according to described physical model, the equation of transfer between each grid in described grid model is set, and determine the initial boundary condition of described grid model.

In one embodiment, according to the inner structure situation of denitrating system, can set up SCR denitrating system internal flow turbulence model, the mass transport model of substance reaction, the porous media model of simulation catalyst layer, and the Dual-Phrase Distribution of Gas olid model of slippage between gas and solid.

Particularly, various models are described below:

(1) turbulence model;

The mobile of SCR denitrating system inside is the turbulent flow of a complexity, considers the reliability of mathematical model and the feasibility of engineering application, can simulate the flow condition of SCR denitrating system inside by selection standard κ-ε two-equation model.

Under rectangular coordinate system, isothermal, can not can be expressed as follows by the baric flow field basic controlling differential equation:

$\frac{\∂\left(\mathrm{\ρu\φ}\right)}{\∂x}+\frac{\∂\left(\mathrm{\ρv\φ}\right)}{\∂v}+\frac{\∂\left(\mathrm{\ρw\φ}\right)}{\∂z}=\frac{\∂}{\∂x}\left({\mathrm{\Γ}}_{\mathrm{\φ}}\frac{\∂\mathrm{\φ}}{\∂x}\right)+\frac{\∂}{\∂y}\left({\mathrm{\Γ}}_{\mathrm{\φ}}\frac{\∂\mathrm{\φ}}{\∂y}\right)+\frac{\∂}{\∂z}\left({\mathrm{\Γ}}_{\mathrm{\φ}}\frac{\∂\mathrm{\φ}}{\∂z}\right)+S_{\mathrm{\φ}}$

In formula,

difference representation speed u, v, w, tubulence energy κ, tubulence energy dissipative shock wave ε, when

the time be continuity equation,

it is the source item caused by gas phase.

Coefficient of diffusion in formula and the concrete form of source item can be in Table one:

Table one

When governing equation is solved, can adopt the fully implicit algorithm SIMPLE algorithm that solves the coupling pressure equation, its calculation procedure is:

1) given initial velocity distribution u0, v0, w0, each coefficient and the constant term of the calculating equation of momentum;

2) given original pressure field p*;

3) solve successively the equation of momentum, obtain and the corresponding speed u* of p*, v*, w*;

4) solve the pressure correction equation and obtain p`, by p`, further improve velocity amplitude;

5) velocity field after utilize improving solves the variable that source item, physical property etc. and velocity field lotus root are closed;

6) velocity field after utilize improving recalculates the coefficient of momentum discrete equation, and by the pressure field after improvement the initial value as next level iterative computation;

Repeat above-mentioned the 3rd to the 6th step, until the velocity field convergence.

(2) mass transport model;

For the mixing of reactionless component, select the chemical substance conservation equation to calculate, adopt the FLUENT technology, estimate the massfraction Y of every kind of material by the convective-diffusive equation of i kind material _i, conservation equation adopts following common version:

$\frac{\∂}{\∂t}\left(\mathrm{\ρ}{Y}_i\right)+\▿\·\left(\mathrm{\ρ}\stackrel{\→}{v}{Y}_i\right)=-\▿{\stackrel{\→}{J}}_i+R_i+S_i$

Wherein, R _ithe clean generation speed of chemical reaction, S _ithe extra generation speed caused for discrete phase and user-defined source item.According to SCR denitrating system technique, NH before catalyzer ₃and NO _xdo not react, only consider both mixing, therefore can be made as zero.The mixing of reactionless component only need be considered the DIFFUSION IN TURBULENCE flux J of i material _i:

${\stackrel{\→}{J}}_i=-(\mathrm{\ρ}{D}_{i,m}+\frac{{\mathrm{\μ}}_t}{{\mathrm{Sc}}_t})\▿Y_i$

While N kind material occurring in system, need to separate the equation of N-1 this form.Because deducting N-1 the massfraction solved by 1, massfraction and mark that be necessary for 1, the N kind material obtain.In order to make the numerical error minimum, N kind material is selected the material of massfraction maximum, selects N while such as oxide, being air ₂.

(3) porous media model;

Porous media model can be applied to a lot of problems, as by being full of the flowing of medium, flowing by filter paper, apertured disk, flow distributor and pipeline heap.Therefore, for the physical model of catalyst layer in network model, can be realized by porous media model.

The equation of momentum of porous medium has additional momentum source item.Source item is comprised of two parts, and a part is viscosity loss item (Darcy), and another is the internal losses item:

$S_i=\underset{j=1}{\overset{3}{\mathrm{\&Sigma;}}}{D}_{\mathrm{ij}}\mathrm{\&mu;}{v}_j+\underset{j=1}{\overset{3}{\mathrm{\&Sigma;}}}{\mathrm{<figure-callout\; id="1"\; label="C\; ij"\; filenames="HDA0000378647350000042.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{ij}}\frac{1}{2}\mathrm{\&rho;}\left|v_j\right|\&CenterDot;v_j$

S wherein _ibe i to (x, y or z) momentum source item, D and C be the regulation matrix.In the porous medium unit, the loss of momentum has contribution for pressure gradient, and pressure drop and fluid velocity (or velocity squared) are proportional.

For simple homogeneous porous medium:

$S_i=\frac{\mathrm{\&mu;}}{\mathrm{\&alpha;}}{v}_i+{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000378647350000042.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\frac{1}{2}\mathrm{\&rho;}\left|v_j\right|v_j$

Wherein α is permeability factor, and C2 is the internal drag factor.

If simulation is perforated plate or pipeline heap, can eliminate the infiltration item and only use internal losses item (Darcy law), at present commercial maximum catalyzer is board-like and honeycomb fashion, this two classes catalyzer can regard as by parallel channels, formed each to the porous medium of the same sex not, its coefficient of internal drag in the flow of flue gas direction can be obtained by test or actual measurement.

(4) Dual-Phrase Distribution of Gas olid model;

In the FLUENT technology, in the basic model of processing the gas-solid two-phase commonly used have four kinds, respectively: without slippage continuum Model, little slippage continuum Model, slippage---many continuum Model of diffusion, and the Separate granule group model trajectory.First three common feature of planting mathematical model is to regard that continuous medium processes as the particle swarm disperseed is the same with fluid-phase, and the motion of examination particle swarm and fluid in Eulerian coordinates system.The discrete particles model trajectory is to describe the movement locus of particle with Lagrangian method.When the flying dust that calculates SCR denitrating system inside distributes, because the volumetric concentration of ash particle is also little, the hypothesis of continuous medium is inapplicable, so this paper is used discrete particles model trajectory (DPM) in processing particle.

This model is assumed to be substantially:

1) fluid-phase is regarded continuous medium as, and Particle Phase is counted as with fluid-phase slippage is arranged, along the dispersion group of self orbital motion;

2) particle self is without DIFFUSION IN TURBULENCE, turbulent viscosity;

3) particle swarm is by the original dimension grouping;

4) each particle swarm along orbital motion separately, do not interfere with each other, do not collide mutually;

5) quality of particle swarm convection cell, momentum and energy influence each other, and to be used as be that certain continuous distribution of equal value is in substance source, the momentum source of multinomial fluid space;

6) second phase volume fraction is less than 10～12%.

During simulation two-way coupling process, at first calculate the external phase flow field of convergence or part convergence, and then create the injection source calculating that is coupled.Take turns the calculating of discrete phase at each, count particles track and upgrade alternate momentum, heat and the mass exchange item in each fluid calculation unit.Then, these exchange items will be applied to the calculating of external phase subsequently.When calculating, coupling in the process of external phase iterative computation, according to certain iterative steps interval, calculates the discrete phase iteration.Until the Flow Field Calculation result of external phase no longer strengthens along with iterative steps and changes, coupling is calculated and just can be stopped, and when reaching convergence, the track of discrete phase also no longer changes.

In one embodiment, for the setting of initial and boundary condition, take boiler BMCR operating mode as examining or check object (design coal), Gas Parameters as shown in Table 2:

Table two

In calculating, NOx is with NO ₂calculated the NH3 amount of feeding and NO ₂molar ratio be 0.8, NH3/ dilution air=1/19(volume ratio), the fly ash granule particle diameter is considered as being uniformly distributed (20 μ m), according to the generalized case of operation, can get flying dust bulk density 750kg/m3.In solution procedure, Turbulent Kinetic, Turbulent Kinetic dissipative shock wave, the equation of momentum, convective-diffusive equation all adopt second order windward method of difference to calculate, and pressure and speed coupling adopt the SIMPLE algorithm.

Step S104, carry out site test to the SCR denitrating system, obtains the Gas Parameters of the on-the-spot operation of SCR denitrating system.

In this step, be that the SCR denitrating system is carried out to site test, obtain the Gas Parameters of the on-the-spot operation of SCR denitrating system, thus can be for carry out the calculation of parameter of computing as grid model.

Step S105, import described grid model by described Gas Parameters and carry out simulation reaction, obtains the duty parameter of SCR denitrating system operation.

In this step, by grid model simulation reaction process, so just can avoid adopting the simulation of being correlated with of real reaction device, both can reduce cost, simultaneously, also can utilize grid model to carry out the reaction simulation under some extreme conditions, thereby can obtain the duty parameter of SCR denitrating system operation.

Step S106, be optimized the on-the-spot operational factor of SCR denitrating system according to described duty parameter.

In this step, obtain parameter by simulation, can provide reference for on-the-spot SCR denitrating system parameter control etc., realization is optimized the on-the-spot operational factor of SCR denitrating system, has reduced Cost optimization, has improved efficiency, in addition, also can carry out fault simulating test, the prediction malfunction, trouble saving occurs.

Along with the demand of SCR device increases day by day, the time of make its design, processing, installing reduces day by day, and the application of numerical simulation in the SCR technology seems more and more important.By technology of the present invention, adopt numerical simulation means to carry out comprehensive optimization analysis to Chinese large-sized station boiler SCR denitrating system, the numerical simulation means dirigibility is relatively good, can revise in time it, its result is preserved and is quoted than being easier to, the inlet boundary condition of numerical simulation can change very flexibly, and its adaptability of estimating the SCR denitrating system also also is more prone to compared with cold test.For the design of raising SCR denitrating system, operation, optimization provide a kind of technological means, can further form SCR denitrating system Numerical Simulation Program storehouse simultaneously, there is stronger learning value and future in engineering applications.

In actual applications, mainly around Flow Field Distribution and the ammonia CONCENTRATION DISTRIBUTION of the A shown in Fig. 1, two faces of B, simulated, and the analyzing influence factor, and then inner structure is optimized.

For more clear its effect, below in conjunction with accompanying drawing and relevant form, set forth the related conclusions in some simulations.

(1) spray ammonia grid entrance section flue gas flow field distribution parameter;

Spray ammonia grid entrance section flue gas flow field distribution situation can find out from Fig. 3 and table three that referring to shown in Fig. 3 and table three before the AIG grid, Flow Field Distribution is more even in most zones.The about 16.44m/s of cross section air-flow maximal rate, be positioned near near the wall of reactor body; Minimum speed is 12.39m/s, is positioned near the wall that deviates from the reactor body side, and AIG entrance section place face mean air flow speed is the maximum relative deviation of 14.78m/ cross section gas velocity approximately 14.86%, mean relative deviation approximately 4.3%, and relative standard deviation is 5.33%.

Table three

Average velocity	m/s	14.78
			Maximal rate	m/s	16.44
Minimum speed	m/s	12.39
			The maximum relative deviation of speed	%	14.86
The speed mean relative deviation	%	4.3
			The speed relative standard deviation	%	5.33

(2) catalyst layer entrance section flue gas flow field distribution parameter;

Catalyst layer entrance section flue gas flow field distribution situation is shown in Figure 4, shown in ASSOCIATE STATISTICS reference table four.By Fig. 4 and table four, can be found out, cross section B speed is all between 3.24～4.69m/s, and with respect to the mean air flow speed of the about 3.85m/s in this cross section, its velocity distribution is well-proportioned.Notice simultaneously occur minimum speed and the maximal rate zone all very little, therefore can think, the uniform characteristic of B face velocity is comparatively desirable.Statistics obtains, and the speed mean relative deviation is 1.98%, and the speed relative standard deviation is 3.29%, can meet the requirement of catalyst inlet flue gas flow rate deviation<± 15%.

Table four

Average velocity	m/s	3.85
			Maximal rate	m/s	4.69
Minimum speed	m/s	3.24
			The speed mean relative deviation	%	1.98
The speed relative standard deviation	%	3.29

On cross-sectional width center line Z=0 and degree of depth center line X=0 two center lines, as shown in Figure 5, as can be seen from Figure 5, flow field, catalyst inlet cross section distributes very even in width Z direction velocity distribution; Depth direction approximately 90% regional Flow Field Distribution is even, but is approximately forming at a high speed local in 6% zone near reactor body outer side surface place.In the numerical evaluation of the former denitration project of this phenomenon and Modelling Test result, exist equally; analyzing reason is caused by this body structure of reactor: there is ramp structure in the rectifier top; overstock and form partial high pressure at the end air-flow; and then make air-flow produce and accelerate at this place; but can be known by figure; this zone is less, on whole flow field, can not produce large impact.

(3) catalyst inlet cross section ammonia CONCENTRATION DISTRIBUTION parameter;

Catalyst inlet cross section ammonia CONCENTRATION DISTRIBUTION situation is shown in Figure 6, shown in ASSOCIATE STATISTICS reference table five:

Table five

The NH3 mean concentration	ppm	119.7
			The NH3 Cmax	ppm	125.5
The NH3 Cmin	ppm	114.3
			Average N H3/NOx(molar concentration rate)	－	0.798

Maximum NH3/NOx(molar concentration rate)	－	0.8369
			Minimum NH3/NOx(molar concentration rate)	－	0.7622
The maximum relative deviation of concentration	%	4.88
			The concentration mean relative deviation	%	2.39
The relative concentration standard deviation	%	2.74

At NH ₃/ NO _xunder the initial boundary condition that mol ratio is 0.8, calculate B cross section NH ₃/ NO _xmean value approximately 0.798, maximal value is 0.8369, minimum value is 0.7622; The maximum relative deviation of ammonia CONCENTRATION DISTRIBUTION is 4.88%, and mean relative deviation is 2.39%, and relative standard deviation is 2.74%; Wherein the maximum relative deviation of ammonia concentration meets the requirement of technical protocol<5%.

(4) reactor flying dust concentration parameter;

The SCR denitrating system of general large-scale coal-fired power station boiler all adopts high flying dust to arrange, flue gas when the catalyzer with a large amount of fly ash granules, fly ash granule likely in catalyst surface deposition, put up a bridge, also exist problems such as the wearing and tearing of catalyzer and obstructions simultaneously.Can obtain movement locus and the CONCENTRATION DISTRIBUTION of flying dust in reactor by the Dual-Phrase Distribution of Gas olid numerical evaluation, predict exactly the flying dust distribution character of inside reactor, contribute to optimal design and operation to reactor.

Shown in Figure 7, Fig. 7 is catalyst inlet cross section B flying dust CONCENTRATION DISTRIBUTION schematic diagram, in Fig. 7, can find out, catalyst inlet flying dust CONCENTRATION DISTRIBUTION is comparatively even generally, still due to the kinetic characteristic of flying dust self, there will be the phenomenon of reuniting among a small circle; And, due to the inertial force effect, near flying dust relative concentration adherent is larger, near kernel of section, flying dust concentration is less.Therefore in actual motion, should strengthen every layer of catalyst inlet and blow ash near adherent.

Shown in Figure 8, Fig. 8 sprays into the track following schematic diagram of particle in reactor on the diverse location grid surface.As seen from Figure 8, flying dust is all better to the followability of air-flow, and particle is along economizer depth direction incoming position difference, and the characteristics of motion obtained is also different.In the reactor-side away from the SCR denitrating system, particle can be with gas shock bottom ash bucket, and then may be caught by ash bucket; Near reactor-side, the particle ash bucket of substantially getting along well produces and occurs simultaneously, and particle is more difficult to be caught by ash bucket.In calculating, examination total particle number is 8379, each ash bucket is caught to fly ash granule and added up, and result is as shown in following table six:

Table six

?	Economizer hopper 1	Economizer hopper 2	Amount to
				Catch granule number	122	165	287
Account for total ash amount number percent %	1.46	1.97	3.43

Ash bucket is 3.43% to total benefit rate of catching of flying dust, and wherein second group of ash bucket of economizer is effective to grey seizure than first group of ash bucket of economizer to grey seizure effect.

The above embodiment has only expressed several embodiment of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to the scope of the claims of the present invention.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection domain of patent of the present invention should be as the criterion with claims.

Claims (8)

1. the on-the-spot operation of a SCR denitrating system optimization method, is characterized in that, comprises the steps:

The geometric center of SCR denitrating system reactor body of take is true origin, builds the three-dimensional model of SCR denitrating system;

According to the architectural feature of SCR denitrating system, described three-dimensional model is carried out to grid division and obtain grid model;

Set up the physical model of SCR denitrating system inner structure, according to described physical model, the equation of transfer between each grid in described grid model is set, and determine the initial boundary condition of described grid model;

The SCR denitrating system is carried out to site test, obtain the Gas Parameters of the on-the-spot operation of SCR denitrating system;

Described Gas Parameters is imported to described grid model and carry out simulation reaction, obtain the duty parameter of SCR denitrating system operation;

According to described duty parameter, the on-the-spot operational factor of SCR denitrating system is optimized.

2. the on-the-spot operation of SCR denitrating system according to claim 1 optimization method, is characterized in that, the described architectural feature according to the SCR denitrating system is carried out to described three-dimensional model the step that grid division obtains grid model and comprised:

According to the architectural feature of SCR denitrating system inside, adopt structuring and non-structured hybrid grid to be divided zoning.

3. the on-the-spot operation of SCR denitrating system according to claim 1 optimization method, is characterized in that, the described step that adopts structuring and non-structured hybrid grid to be divided zoning comprises:

By the flue of the zoning of three-dimensional model, and reactor part with structured grid, divided, and by the flue fair water fin of the zoning of three-dimensional model, and the reactor inlet part with unstructured grid, divided.

4. according to the on-the-spot operation of the described SCR denitrating system of claim 2 or 3 optimization method, it is characterized in that, total grid number of described grid model is 1,500,000.

5. the on-the-spot operation of SCR denitrating system according to claim 1 optimization method, is characterized in that, the step of the physical model of the described SCR of foundation denitrating system inner structure comprises:

Set up SCR denitrating system internal flow turbulence model, the mass transport model of substance reaction, the porous media model of simulation catalyst layer, and the Dual-Phrase Distribution of Gas olid model of slippage between gas and solid.

6. the on-the-spot operation of SCR denitrating system according to claim 1 optimization method, is characterized in that, the equation of transfer of described SCR denitrating system internal flow turbulence model is the companied with k-s two-equation model.

7. the on-the-spot operation of SCR denitrating system according to claim 1 optimization method, is characterized in that, describedly described Gas Parameters is imported to described grid model carries out simulation reaction, and the step of obtaining the duty parameter of SCR denitrating system operation comprises:

Equation of transfer corresponding to each physical model by the described grid model of described Gas Parameters substitution, solve described equation of transfer, obtains the described SCR denitrating system inside duty parameter in operational process at the scene.

8. optimization method is moved at SCR denitrating system according to claim 1 scene, it is characterized in that, described duty parameter comprises: spray ammonia grid entrance section flue gas flow field distribution parameter, catalyst layer entrance section flue gas flow field distribution parameter, catalyst inlet cross section ammonia CONCENTRATION DISTRIBUTION parameter, and/or reactor flying dust concentration parameter.

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